TITLE: GCN CIRCULAR NUMBER: 16180 SUBJECT: GRB 140428A: Keck detection of a red optical afterglow candidate DATE: 14/04/29 07:23:15 GMT FROM: Daniel Perley at Caltech D. A. Perley (Caltech) reports: I observed the position of GRB 140428A (Kocevski et al., GCN 16177; Page et al., GCN 16178) using LRIS on the Keck I 10-meter telescope. A single 150-second imaging exposure was acquired simultaneously in both g and i filters. An faint source is well-detected inside the XRT error circle in the i-band image at the following location (J2000): RA = 12:57:28.392 dec = +28:23:06.28 However, the object is completely absent in g-band. Photometry relative to SDSS gives magnitudes of: g > 26.42 i = 23.55 +/- 0.07 at a time of 06:09:30 UT (2014-04-29), 7.478 hours after the GRB trigger. If this corresponds to the afterglow of the GRB, the red color suggests either a (moderately) high-redshift or dust-extinguished event. Further observations are planned.